Retinal detachment with subsequent loss of vision is a major clinical problem associated with a number of ocular diseases, including proliferative vitreoretinopathy (PVR) and proliferative diabetic retinopathy (PDR). Surgery, the only treatment currently available, has a high rate of recurrence of fibrous epiretinal membrane formation and retinal detachment. Smooth muscle (SM) alpha-actin containing myofibroblasts are a major cell type present in the epiretinal membranes that form in PVR and PDR and it is these cells that are responsible for generation of force leading to retinal detachment. The long-term goal of this research is to develop a gene therapy-based approach that targets and blocks the contraction of the myofibroblast. The first objective of this project is to develop a myofibroblast-specific promoter. Recent studies have suggested that the regulation of SM alpha-actin expression is different in myofibroblasts and smooth muscle cells and these studies have begun to identify regulatory elements in the promoter bf SM alpha-actin that might be responsible for these differences. Therefore, the first specific aim is to identify regulatory elements within the SM alpha-actin promoter that are specific to myofibroblasts in epiretinal membranes. To address this aim we will use transgenic mice containing a SM alpha-actin promoter/LacZ transgene in which specific regulatory elements have been deleted or mutated. These mice will be mated with a transgenic mouse model in which an epiretinal membrane containing myofibroblasts forms and contracts, with subsequent retinal detachment. The second part of our long-term goal is to be able to block the contraction of myofibroblasts in the epiretinal membranes. The expression of SM alpha-actin in myofibroblasts is functionally related to the ability of these cells to generate large amounts of contractile force. Therefore, the second specific aim is to determine whether knocking out the SM alpha-actin gene will decrease or inhibit retinal detachment. Specifically we will determine the length of time it takes for retinal detachment to occur in control and SM alpha-actin-null mice. These studies will provide the basis for developing a gene therapy-based approach that can specifically target myofibroblasts in epiretinal membranes and block their generation of contractile force thereby blocking epiretinal membrane contraction and retinal detachment.